import React from 'react';
import ReactDOM from 'react-dom';
import './index.css';

function Square(props){

      return (
        <button className="square" 
        onClick={() => props.onClick() }
        >
          {props.value}
        </button>
      );
  }
  
  class Board extends React.Component {

    renderSquare(i) {
      return (<Square value={this.props.squares[i]} 
      onClick={() => this.props.onClick(i)} />);
    }
  
    render() {
      return (
        <div>
          {/* <div className="status">{status}</div> */}
          <div className="board-row">
            {this.renderSquare(0)}
            {this.renderSquare(1)}
            {this.renderSquare(2)}
          </div>
          <div className="board-row">
            {this.renderSquare(3)}
            {this.renderSquare(4)}
            {this.renderSquare(5)}
          </div>
          <div className="board-row">
            {this.renderSquare(6)}
            {this.renderSquare(7)}
            {this.renderSquare(8)}
          </div>
        </div>
      );
    }
  }
  
  class Game extends React.Component {

    constructor(props){
      super(props);
      this.state={
        history: [{
          squares: Array(9).fill(null),
        }],
        stepNumber: 0,
        xIsNext: true,
      };
    }

    handleClick(i){
      const history=this.state.history.slice(0, this.state.stepNumber + 1);
      const current = history[history.length - 1];
      const squares = current.squares.slice();
      
      if(calculateWinner(squares) || squares[i]){
        // do nothing
        return;
      }
      squares[i]=this.state.xIsNext?'X':'O';
      this.setState({
        history: history.concat([{
          squares: squares,
        }]),
        stepNumber: history.length,
        xIsNext: !this.state.xIsNext,
      });
    }

    jumpTo(step) {
      this.setState({
        stepNumber: step,
        xIsNext: (step % 2) === 0,
      });
    }

    render() {
      const history=this.state.history;
      const current=history[this.state.stepNumber];
      const winner=calculateWinner(current.squares);

      let status;
      if(winner){
        status='Winner: '+winner;
      }else{
        status = 'Next player: '+(this.state.xIsNext?'X':'O');
      }

      const moves = history.map((move, step) => {
        const desc = step ?
          'Go to move #' + step :
          'Go to game start';
        return (
          <li key={step}>
            <button onClick={() => this.jumpTo(step)}>{desc}</button>
          </li>
        );
      });

      return (
        <div className="game">
          <div className="game-board">
            <Board squares={current.squares} 
            onClick={(i) => this.handleClick(i)}/>
          </div>
          <div className="game-info">
            <div>{status}</div>
            <ol>{moves}</ol>
          </div>
        </div>
      );
    }
  }
  
  // ========================================
  
  ReactDOM.render(
    <Game />,
    document.getElementById('root')
  );

  function calculateWinner(squares) {
    const lines = [
      [0, 1, 2],
      [3, 4, 5],
      [6, 7, 8],
      [0, 3, 6],
      [1, 4, 7],
      [2, 5, 8],
      [0, 4, 8],
      [2, 4, 6],
    ];
    for (let i = 0; i < lines.length; i++) {
      const [a, b, c] = lines[i];
      if (squares[a] && squares[a] === squares[b] && squares[a] === squares[c]) {
        return squares[a];
      }
    }
    return null;
  }
  